NO. 3652 ISOPODA AND TANAIDACEA—MILLER 33 
The foregoing comparison is rather crude, as no distinction was 
made between benthic and pelagic groups of amphipods and isopods. 
Natatory isopods, notably sphaeromatids and idoteids are represented 
much better in the buoy collection than predominantly crawling 
forms such as anthurids and tanaidaceans. Further, it is significant 
that bottom-dwelling isopods and tanaidaceans were taken generally 
from the anchor or from lower on the chain than more pelagic species, 
which were found higher on the chain and on the buoy itself, often 
at or near the waterline (table 2). More than half of the occurrences 
of sphaeromatids and idoteids were within the first meter below the 
waterline, and about three-fourths of them were within the first 
five meters below the surface. On the other hand, no anthurid was 
found less than 10 meters from the surface, and more than half of 
the occurrences of tanaidaceans were below five meters, with only 
17 percent within the first meter from the surface. The fairly high 
incidence of janirid isopods, which are not noted for their swimming 
ability, may be associated with the fact that they often cling to 
floating seaweed, as do many of the better swimmers. Currents 
doubtless transport swimming or floating crustaceans considerable 
distances and may waft them against buoys. 
If locomotor ability were solely responsible for differences between 
eroups in incidence and distribution in buoys, one should expect 
that benthic caprellids and corophiids would be less abundant than 
natatory amphipods. Unfortunately, the amphipods of the buoy 
collections have not been worked up sufficiently for such comparisons. 
The impression gained from collecting and sorting, however, is that 
caprellids are as well represented on buoys as natatory gamma- 
rideans—if not more so. 
DisrERsAL.—As was expected, most of the isopods and tanaidaceans 
taken from buoys belong to indigenous or to cosmopolitan species 
known to occur in the region. There were, of course, many new locality 
records within previously established limits. In some instances, how- 
ever, known geographic ranges were extended, especially in regions 
that have not been surveyed adequately for these crustaceans. Many 
extensions were for relatively short distances and of no great biological 
significance. Some species, however, were found at stations far from 
any previously recorded locality. Extralimital species are of special 
interest in relation to means of dispersal and establishment of intro- 
duced species in new regions. Several noteworthy examples are discussed 
below, including Sphaeroma walkeri and S. terebrans, Idotea balthica 
and J. metallica, and Carpias bermudensis. 
The discovery of Sphaeroma walkeri in several widely separated 
localities in Florida and in the Hawaiian Islands was surprising as 
this species has never before been reported from the central Pacific 
281-333—68——3 
